Electric discharge machining device and electric discharge machining method

ABSTRACT

An electric discharge machining apparatus is provided with an electrode mounting section which mounts a tool electrode, and an electrode driving section which has a radial driving section which supports and drives the electrode mounting section in a non-contact manner in a radial direction and a thrust driving section which supports and drives the electrode mounting section in a non-contact manner in a thrust direction, and a machining state is controlled by adjusting a position of the tool electrode by the electrode driving section. Because of such a structure, a mass increase of a section which should be driven together with the electrode is restricted, and high response in X-axis, Y-axis and Z-axis directions are achieved, whereby an electric discharge machining apparatus capable of improving a machining speed and a machining accuracy is achieved.

TECHNICAL FIELD

[0001] The present invention relates to a method of and an apparatus forelectric discharge machining in which a voltage is applied between atool electrode and a workpiece so as to generate an electric dischargeand execute machining (“working”). More particularly, this inventionrelates to a method of and an apparatus for electric discharge machiningwhich can achieve a high speed response in X-axis, Y-axis and Z-axisdirections for driving an electrode, and can intend to improve amachining accuracy.

BACKGROUND ART

[0002] In electric discharge machining, a tool electrode and a workpieceare arranged in a machining fluid, a voltage is applied therebetween andan electric discharge is generated so as to erode the workpiece. In anelectric discharge machining apparatus, in order to machining a desiredshape while maintaining a stable machining state, a driving apparatuswhich adjusts positions of the tool electrode or the workpiece isprovided. FIG. 17 is a schematic view which shows an outline structureof a conventional electric discharge machining apparatus which isdescribed, for example, in pages 63-64 of “Discharge MachiningTechnique—From Basics to Future Development” issued by Nikkan KogyoShinbun, Ltd (1997).

[0003] In FIG. 17, reference numeral 101 denotes a tool electrode,reference numeral 102 denotes a workpiece, reference numeral 103 denotesa machining fluid, reference numeral 104 denotes a machining tank,reference numeral 1201 denotes an electrode mounting section whichmounts the tool electrode 101, reference numeral 501 denotes a headsection which supports the electrode mounting section 1201, referencenumeral 502 denotes a head drive section which drives the tool electrode101, the electrode mounting section 1201 and the head section 501,reference numeral 503 denotes a column section, reference numeral 504denotes a column driving section which drives the tool electrode 101,the electrode mounting section 1201, the head section 501, the headdriving section 502 and the column section 503, reference numeral 505denotes a saddle section, reference numeral 506 denotes a saddle drivingsection which drives the tool electrode 101, the electrode mountingsection 1201, the head section 501, the head driving section 502, thecolumn section 503, the column driving section 504 and the saddlesection 505, and reference numeral 507 denotes a bed section. The headdriving section 502, the column driving section 504 and the saddledriving section 506 are, for example, constituted by an AC motor and aball screw, and respectively constitute a driving section whichpositions the electrode in Z direction, a driving section whichpositions in Y direction and a driving section which positions in Xdirection. Further, reference numeral 119 denotes a machining powersupply which supplies a machining energy to the tool electrode 101 andthe workpiece 102, reference numeral 120 denotes a machining statedetecting apparatus which detects a machining state, reference numeral1202 denotes a servo amplifier which supplies a drive current to each ofthe electrode mounting section 1201, the head driving section 502, thecolumn driving section 504 and the saddle driving section 506 so as toexecute positioning, and reference numeral 1203 denotes a controlapparatus giving a command value to the servo amplifier 1202 and themachining power supply 119. Further, reference numeral 122 denotes anelectric discharge machining process progressed between the toolelectrode 101 and the workpiece 102.

[0004]FIG. 18 shows a gap control system which controls machining statein the electric discharge machining apparatus shown in FIG. 17. In FIG.18, reference numeral 301 denotes an electric discharge machiningprocess section, reference numeral 302 denotes a machining statedetecting section, reference numeral 303 denotes a reference valuesetting section, reference numeral 304 denotes a machining pass settingsection, reference numeral 1301 denotes a machining control section,reference numeral 1302 denotes a XYZ driving control section, referencenumeral 1303 denotes a current amplifier section, reference numeral 1304denotes a XYZ driving section, and reference numeral 1305 denotes a XYZdriving apparatus constituted by the XYZ driving control section 1302,the current amplifier section 1303 and the XYZ driving section 1304. Theelectric discharge machining process section 301 corresponds to theelectric discharge machining process 122, the machining state detectingsection 302 corresponds to the machining state detecting apparatus 120,the XYZ driving control section 1302 and the current amplifier section1303 correspond to the servo amplifier 1202, and the XYZ driving section1304 corresponds to the head driving section 502, the column drivingsection 504 and the saddle driving section 506, respectively. Further,the reference value setting section 303, the machining pass settingsection 304 and the machining control section 1301 are constructed inthe control apparatus 1203. Further, y indicates a state variable of theelectric discharge machining process, ym indicates a detected valuedetected by the machining state detecting section 302, r indicates areference value set by the reference value setting section 303, eindicates a deviation determined from the reference value r and thedetected value ym, Rp indicates a machining pass vector set by themachining pass setting section 304, Up indicates a position commandvalue to the XYZ driving control section 1302, Uc indicates a currentcommand value to the current amplifier section 1303, Ic indicates acurrent amount supplied to the XYZ driving section 1304, St indicates aposition detected value obtained from the XYZ driving section 1304, andMp indicates an electrode position operating amount operated by the XYZdriving section 1304. The position command value Up to the XYZ drivingcontrol section 1302 is determined by the machining control section 1301on the basis of the deviation e and the machining pass vector Rp. Sincethe machining pass vector Rp is given by a Cartesian coordinate system(XYZ), the position command value Up is in the same Cartesian coordinatesystem (XYZ). Further, the position detected value St is the detectedvalue in the X direction, the Y direction and the Z direction.Accordingly, in the XYZ driving control section 1302, the positioncommand value Up and the position detected value St are compared, andthe current command value Uc to the current amplifier section 1303 isdetermined. The current command value Uc is given to each of threecurrent amplifiers for the head driving section 502, the column drivingsection 504 and the saddle driving section 506. That is, in theconventional gap control system shown in FIG. 18, it is made such as todetect, for example, an average gap voltage by the machining statedetecting section 302, and move the tool electrode by the XYZ drivingapparatus 1305 so that the detected value coincides with a predeterminedreference value, thereby achieving a stable machining state.

[0005] However, the machining state irregularly changes, and in order tomaintain a stable machining state, a high speed response of the XYZdriving apparatus becomes important. When a stable machining state cannot be maintained, a short-circuit state, a continuous arc state or thelike is frequently generated, and an effective electric dischargingstate contributing to the machining is reduced, so that the machiningspeed is reduced. Further, since the short-circuit state, the continuousarc state or the like is frequently generated, a crack or a pit isformed on the machined surface, or an abnormal wear of a tool electrodeis locally generated, so that a reduction of machining surface qualityor a deterioration of machining accuracy is caused. When a high speedresponse of the XYZ driving apparatus can not be expected, since it isintended to maintain a stable machining state by selecting the machiningcondition in which a gap distance during machining becomes comparativelylarge, it is hard to achieve the machining at high accuracy.

[0006] The Patent Publication of Japanese Patent No. 2714851 “DischargeMachining Control Device” discloses a technology for solving theproblems in the high speed response of the tool electrode drivingapparatus explained above. It is disclosed in this publication, in orderto control a gap between a tool electrode and a workpiece, to constitutea driving system by assembling a plurality of driving mechanisms havingdifferent frequency characteristics and moving at least one of the toolelectrodes and the workpiece in a coaxial direction. However, thispublication does not describe a particular driving mechanism which canachieve a high speed response in all directions of the X direction, theY direction and the Z direction, and there is not referred to amachining control method or a control apparatus when accompanying with ajump motion or a planetary motion which is used for maintaining thestable machining state.

[0007] Further, in the grinding method disclosed in Japanese PatentApplication Laid-Open No. H1-234162 (Japanese Application), there ispresented a method of executing a cutting motion of a tool to aworkpiece at a high speed by providing a magnetic bearing spindle andmoving the spindle in a spindle diametrical direction on the basis of apredetermined reference value, in place of a cutting motion of aconventional tool constituted by a motor and a ball screw to theworkpiece, in a grinding machine, whereby a machining efficiency and amachining accuracy can be improved. In the electric discharge machining,it is necessary that the tool electrode is driven in the XYZ directionson the basis of the machining pass, and a driving amount is determinedon the basis of the electric discharge machining state so that themachining becomes stable. Further, there is such when the driving amountbecomes some μm to some tens cm in case of some machinings, and there issuch when the machining can not be executed when there is employed thedrive amount which can be driven by the magnetic bearing spindle. Thatis, in accordance with the machining method shown in Japanese PatentApplication Laid-Open No. H1-234162 mentioned above, since the structureis not made such as to control the driving direction, it is hard toobtain a good machining result even when being applied to the electricdischarge machining.

[0008] In the conventional electric discharge machining apparatus, whendriving the tool electrode 101 to each of the X-axis, the Y-axis and theZ-axis directions, it is necessary that the head driving section 502drives the electrode mounting section 1201 and the head section 502 inaddition to the tool electrode 101 in the Z-axis direction, the columndriving section 504 drives the electrode mounting section 1201, the headsection 501, the head driving section 502 and the column section 503 inaddition to the tool electrode 101 in the Y-axis direction, and thesaddle driving section 506 drives the tool electrode 101, the electrodemounting section 1201, the head section 501, the head driving section502, the column section 503, the column driving section 504 and thesaddle section 505 in the X-axis direction. Accordingly, in order toachieve the response in each of the driving sections, there is a problemthat it is necessary to take into consideration an increase of mass ofthe sections moving in each of the X-axis, the Y-axis and the Z-axisdirections together with the tool electrode 101 in addition to the toolelectrode 101. The response here becomes a relation response of the headdriving section 502>response of the column driving section 504>responseof the saddle driving section 506, and the control performance of themachining state is determined on the basis of the response of the saddledriving section 506, so that there is generated an obstacle in view ofimproving the machining speed and the machining accuracy.

[0009] The present invention has been achieved in order to solve theproblems as mentioned above. It is an object of this invention is toprovide a method of and apparatus for electric discharge machining whichcan restrict an increase of mass of sections which are required to movein each of X-axis, Y-axis and Z-axis directions together with a toolelectrode, which can achieve a high speed response in the X-axis, theY-axis and the Z-axis directions, and which can improve machining speedand machining accuracy.

DISCLOSURE OF THE INVENTION

[0010] According to a first aspect of the present invention, there isprovided an electric discharge machining apparatus comprising anelectrode mounting unit which mounts a tool electrode, an electrodedriving unit which has a radial driving unit which drives the electrodemounting unit in a non-contact manner in a radial direction and a thrustdriving unit which drives the electrode mounting unit in a non-contactmanner in a thrust direction, a machining state detecting unit whichdetects an electric discharge machining state, a reference value settingunit which sets a control reference of the electric discharge machiningstate, a machining pass setting unit which sets a machining pass, and amachining control unit which adjusts a position of the tool electrode bythe electrode driving unit while taking into consideration the machiningpass set by the machining pass setting unit, so that the detected valuedetected by the machining state detecting unit coincides with thereference value set by the reference value setting unit. Accordingly, itis possible to restrict a mass increase in the sections which should bedriven together with the tool electrode, and to achieve the high speedresponse in the X-axis, the Y-axis and the Z-axis directions of theelectrode driving, it is possible to maintain a stable machining stateeven when the machining state irregularly changes, and it is possible toobtain an effect of improving the machining speed and the machiningaccuracy.

[0011] A second aspect of the present invention provides an electricdischarge machining apparatus comprising an electrode mounting unitwhich mounts a tool electrode, an electrode driving unit which has aradial driving unit which drives the electrode mounting unit in anon-contact manner in a radial direction and a thrust driving unit whichdrives the electrode mounting unit in a non-contact manner in a thrustdirection, a position adjusting unit which adjusts a position of theelectrode driving unit or a workpiece, a machining state detecting unitwhich detects an electric discharge machining state, a reference valuesetting unit which sets a control reference of the electric dischargemachining state, a machining pass setting unit which sets a machiningpass, and a coordination control unit which adjusts a relative positionbetween the tool electrode and the workpiece by coordinating theelectrode driving unit with the position adjusting unit while takinginto consideration the machining pass set by the machining pass settingunit, so that the detected value detected by the machining statedetecting unit coincides with the reference value set by the referencevalue setting unit. Accordingly, it is possible to achieve the highspeed response in the X-axis, the Y-axis and the Z-axis directions ofthe electrode driving, it is possible to achieve a stable machiningstate even when the machining state irregularly changes, and it ispossible to obtain an effect of improving the machining speed andimproving the machining accuracy without being affected by thelimitation of the driving stroke of the electrode driving section byadjusting the position of the electrode driving apparatus by theposition adjusting apparatus following to the progress of the machining.

[0012] A third aspect of the present invention provides the electricdischarge machining apparatus according to the second aspect, whereinthe coordination control unit has a jump motion control unit whichexecutes a jump motion by the position adjusting unit. Accordingly, itis possible to achieve the high speed response in the X-axis, the Y-axisand the Z-axis directions of the electrode driving. Moreover, it ispossible to machine while forcibly discharging any debris staying in themachining gap because of the jump motion so that it is possible toobtain an effect of improving the machining speed and improving themachining accuracy even when the machining depth is increased. Moreover,the machining is not limited by the driving stroke of the electrodedriving unit.

[0013] A fourth aspect of the present invention provides the electricdischarge machining apparatus according to the second aspect, whereinthe coordination control unit has a planetary motion control unit whichexecutes a planetary motion by the electrode driving unit. Accordingly,it is possible to maintain a more stable machining with planetary motionon the basis of the high speed response in the X-axis, the Y-axis andthe Z-axis directions, and it is possible to obtain an effect ofimproving the machining speed and the machining accuracy.

[0014] A fifth aspect of the present invention provides the electricdischarge machining apparatus according to the second aspect, whereinthe coordination control unit has a jump motion control unit whichexecutes a jump motion by the position adjusting unit and a planetarymotion control unit which executes a planetary motion by the electrodedriving unit. Accordingly, it is possible to achieve the high speedresponse in the X-axis, the Y-axis and the Z-axis directions of theelectrode driving. Moreover, it is possible to machine while forciblydischarging any debris staying in the machining gap because of the jumpmotion so that it is possible to obtain an effect of improving themachining speed and improving the machining accuracy even when themachining depth is increased. Moreover, the machining is not limited bythe driving stroke of the electrode driving unit.

[0015] A sixth aspect of the present invention provides the electricdischarge machining apparatus according to the first aspect and thesecond aspect, wherein the electrode driving unit has a rotation drivingunit which rotates the electrode mounting unit and a rotation detectingunit which detects at least one of an angle of rotation and an angularvelocity of rotation, and the machining control unit or the coordinationcontrol unit has a rotation control unit. Accordingly, it is possible toachieve the high speed response in the X-axis, the Y-axis and the Z-axisdirections of the electrode driving. Moreover, it is possible to machinewhile forcibly discharging, any debris staying in the machining gapbecause of the jump motion so that it is possible to obtain an effect ofimproving the machining speed and improving the machining accuracy evenwhen the machining depth is increased. Moreover, the machining is notlimited by the driving stroke of the electrode driving unit.

[0016] A seventh aspect of the present invention provides an electricdischarge machining method made so as to drive an electrode mountingunit which mounts a tool electrode in a non-contact manner in a radialdirection and drive the electrode mounting unit in a non-contact mannerin a thrust direction, adjust a position of a driving unit or aworkpiece, and adjust a position of the tool electrode with respect tothe workpiece while taking into consideration a set machining pass, sothat a detected value of an electric discharge machining state coincideswith a set reference value of the electric discharge machining state.Accordingly, it is possible to restrict a mass increase in the sectionswhich should be driven together with the tool electrode, and to achievethe high speed response in the X-axis, the Y-axis and the Z-axisdirections of the electrode driving, it is possible to maintain a stablemachining state even when the machining state irregularly changes, andit is possible to obtain an effect of improving the machining speed andimproving the machining accuracy.

[0017] An eighth aspect of the present invention provides an electricdischarge machining method made so as to, drive an electrode mountingunit which mounts a tool electrode in a non-contact manner in a radialdirection and drive the electrode mounting unit in a non-contact mannerin a thrust direction, adjust a position of a driving unit or aworkpiece, and adjust a position of the tool electrode with respect tothe workpiece while taking into consideration a set machining pass, sothat a detected value of an electric discharge machining state coincideswith a set reference value of the electric discharge machining state bycoordinating the driving unit with the adjusting unit. Accordingly, itis possible to achieve the high speed response in the X-axis, the Y-axisand the Z-axis directions of the electrode driving, it is possible toachieve a stable machining state even when the machining stateirregularly changes, and to adjust the position of the electrode drivingapparatus based on the progress of the machining by the positionadjusting apparatus, whereby it is possible to obtain an effect ofimproving the machining speed and improving the machining accuracywithout being affected by the limitation of the driving stroke of theelectrode driving section.

[0018] A ninth aspect of the present invention provides an electricdischarge machining apparatus comprising, an electrode mounting unitwhich has a through hole which inserts a wire-like electrodetherethrough and which has a holding and feeding mechanism of theelectrode, an electrode driving unit which has a thrust driving unitwhich drives the electrode mounting unit at least in a non-contactmanner in a thrust direction, a machining state detecting unit whichdetects an electric discharge machining state, a reference value settingunit which sets a control reference of the electric discharge machiningstate, a machining control unit which adjusts a position of the toolelectrode by the electrode driving unit so that the detected valuedetected by the machining state detecting unit coincides with thereference value set by the reference value setting unit, and anelectrode supply control unit which adjusts holding or feeding of theelectrode. Accordingly, it is possible to achieve the high speedresponse in thrust direction, and it is possible to always maintain astable machining state even when the machining state irregularlychanges.

[0019] A tenth aspect of the present invention provides the electricdischarge machining apparatus according to the ninth aspect, comprisinga tool electrode automatic supplying unit which automatically suppliesthe wire-like electrode to the through hole provided in the electrodedriving unit. Accordingly, in addition to the effects of the ninthaspect, it is possible to continuously and effectively execute a holemachining.

[0020] An eleventh aspect of the present invention provides the electricdischarge machining apparatus according to the ninth aspect or the tenthaspect, wherein the electrode driving unit is provided with a rotationdriving unit which rotates the electrode mounting unit. Accordingly, inaddition to the effects of the ninth aspect or the tenth aspect, it ispossible to perform stable machining by rotating the electrode whenmachining the hole.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a cross sectional view which shows a structure of anelectric discharge machining apparatus corresponding to a firstembodiment of the present invention,

[0022]FIG. 2 is a schematic view which shows an arrangement of anelectromagnet section of an electrode driving section and a positiondetecting section in the electric discharge machining apparatus shown inFIG. 1,

[0023]FIG. 3 is a block diagram which shows a system for controlling agap between a tool electrode and a workpiece in the electric dischargemachining apparatus shown in FIG. 1,

[0024]FIG. 4 is a flow chart which shows an operation content of thesystem shown in FIG. 3,

[0025]FIG. 5 is a schematic view which shows a structure of an electricdischarge machining apparatus corresponding to a second embodiment ofthe present invention,

[0026]FIG. 6 is a block diagram which shows a system for controlling agap between a tool electrode and a workpiece in the electric dischargemachining apparatus shown in FIG. 5,

[0027]FIG. 7 is a block diagram of the system for controlling a gapbetween a tool electrode and a workpiece shown in FIG. 6 in detail,

[0028]FIG. 8 is a flow chart which shows an operation content of thesystem shown in FIG. 5,

[0029]FIG. 9 is a block diagram which shows a part of a system forcontrolling a gap between a tool electrode and a workpiece in anelectric discharge machining apparatus corresponding to a thirdembodiment of the present invention,

[0030]FIG. 10 is a block diagram which shows a part of a system forcontrolling a gap between tool electrode and a workpiece in an electricdischarge machining apparatus corresponding to a forth embodiment of thepresent invention,

[0031]FIG. 11 is a schematic view which shows an electrode driving unitin an electric discharge machining apparatus corresponding to a fifthembodiment of the present invention,

[0032]FIG. 12 is a flow chart which shows a part of a system forcontrolling a gap between tool electrode and a workpiece in the electricdischarge machining apparatus having the electrode driving unit shown inFIG. 11,

[0033]FIG. 13 is a schematic view which shows an outline of an electricdischarge machining apparatus corresponding to a sixth embodiment of thepresent invention,

[0034]FIG. 14 is a block diagram of a gap control system which controlsmachining state in the electric discharge machining apparatus shown inFIG. 13, and an electrode supply control system,

[0035]FIG. 15 is a flow chart which shows an operation content in theelectrode supply control system shown in FIG. 14,

[0036]FIG. 16 is a schematic view which shows an outline of acharacteristic section of another electric discharge machining apparatuscorresponding to the sixth embodiment of the present invention,

[0037]FIG. 17 is a schematic view which shows a conventional electricdischarge machining apparatus, and

[0038]FIG. 18 is a block diagram which shows a system for controlling agap between tool electrode and a workpiece in the electric dischargemachining apparatus shown in FIG. 17.

BEST MODE FOR CARRYING OUT THE INVENTION

[0039] First Embodiment:

[0040]FIG. 1 is a schematic view which shows an outline structure of anelectric discharge machining apparatus corresponding to a firstembodiment of the present invention. In the drawing, reference numeral101 denotes a tool electrode, reference numeral 102 denotes a workpiece,reference numeral 103 denotes a machining fluid, reference numeral 104denotes a machining tank, reference numeral 105 denotes an electrodedriving section, reference numeral 106 denotes an electrode mountingsection which mounts the tool electrode 101, reference numerals 107 and108 denote a radial electromagnetic section which supports and drivesthe electrode mounting section 106 in a non-contact manner in a radialdirection, reference numerals 109 and 110 denote a radial directionposition detecting section which detects a position of the electrodemounting section 106 in a radial direction, reference numerals 111 and112 denote a thrust electromagnet section which supports and drives theelectrode mounting section 106 in a non-contact manner in a thrustdirection, reference numeral 113 denotes a thrust direction positiondetecting section which detects a position of the electrode mountingsection 106 in the thrust direction, reference numerals 114 and 115denote an auxiliary bearing section which auxiliary supports theelectrode mounting section 106, reference numeral 116 denotes aninsulating section corresponding to a part of the electrode mountingsection 106, and reference numeral 117 denotes a power supply sectionwhich supplies a machining current to the tool electrode 101. Further,reference numeral 118 denotes a current amplifier which supplies currentto the electromagnetic section of the electrode driving section 105,reference numeral 119 denotes a machining power supply supplying amachining energy to the tool electrode 101 and the workpiece 102,reference numeral 120 denotes a machining state detecting apparatuswhich detects a machining state, and reference numeral 121 denotes acontrol apparatus which gives a command value to the current amplifier118 and the machining power supply 119. Further, reference numeral 122denotes an electric discharge machining process progressed between thetool electrode 101 and the workpiece 102.

[0041]FIG. 2(A) is a schematic view which shows an arrangement of theradial electromagnet sections 107 and 108 and the radial directionposition detecting sections 109 and 110 in the electrode driving section105. As shown in FIG. 1 and FIG. 2(A), four radial electromagneticsections 107 support the electrode mounting section 106 in a radialdirection from an upper side in a non-contact manner and drive theelectrode mounting section 106. Moreover, four radial electromagnetsections 108 support the electrode mounting section 106 in a radialdirection from a lower side in a non-contact manner and drive theelectrode mounting section 106. Further, corresponding to each of theradial electromagnet sections, four radial direction position detectingsections 109 are arranged on the upper side and four radial directionposition detecting sections 110 are arranged on the lower side. FIG.2(B) is a schematic view which shows an arrangement of the thrustelectromagnet sections 111 and 112 which support and drive the electrodemounting section 106 in a non-contact manner in a thrust direction, andthe thrust direction position detecting section 113 which detects theposition in the thrust direction. As shown in FIG. 1 and FIG. 2(B), twothrust electromagnetic sections 111 and 112 support and drive theelectrode mounting section 106 in a non-contact manner in a thrustdirection. Further, two thrust direction position detecting sections 113are arranged. As mentioned above, a radial driving section which drivesthe tool electrode in the radial direction is constituted by the radialelectromagnet sections 107 and 108 and the radial direction positiondetecting sections 109 and 110, and a thrust driving section whichdrives the tool electrode in the thrust direction is constituted by thethrust electromagnet sections 111 and 112 and the thrust directionposition detecting section 113. It is possible to support the electrodemounting section 106 in a non-contact manner by the above structure, andit is possible to finely drive the tool electrode 101 in the XYZ-axesdirections.

[0042]FIG. 3 is a block diagram of a system for controlling a gapbetween a tool electrode and a workpiece which control the electricdischarge machining state of the electric discharge machining apparatusshown in FIG. 1. In FIG. 3, reference numeral 301 denotes an electricdischarge machining process section, reference numeral 302 denotes amachining state detecting section, reference numeral 303 denotes areference value setting section, reference numeral 304 denotes amachining pass setting section, reference numeral 305 denotes amachining control section, and reference numeral 306 denotes anelectrode driving control section. Reference numeral 307 denotes acurrent amplifier section, reference numeral 308 denotes an electrodedriving section, and reference numeral 309 denotes an electrode drivingapparatus section constituted by the electrode driving control section306, the current amplifier section 307 and the electrode driving section308. The electric discharge machining process section 301 corresponds tothe electric discharge machining process 122, the machining statedetecting section 302 corresponds to the machining state detectingapparatus 120, the current amplifier section 307 correspond to thecurrent amplifier 118, and the electrode driving section 308 correspondsto the electrode driving section 105, respectively.

[0043] Further, the reference value setting section 303, the machiningpass setting section 304, the machining control section 305 and theelectrode driving control section 306 are constructed in the controlapparatus 121. Further, y indicates a state variable of the electricdischarge machining process, ym indicates a detected value detected bythe machining state detecting section 302, r indicates a reference valueset by the reference value setting section 303, e indicates a deviationdetermined from the reference value r and the detected value ym, Rpindicates a machining pass vector set by the machining pass settingsection, Up indicates a command value to the electrode driving controlsection 306, Uc indicates a current command value to the currentamplifier section 307, Ic indicates a current amount supplied to theelectrode driving section 308, Sm indicates a position detected valueobtained from the electrode driving section 308, and Mp indicates anelectrode position operating amount operated by the electrode drivingsection 308.

[0044] The position command value Up to the electrode driving controlsection 306 is determined by the machining control section 305 on thebasis of the deviation e and the machining pass vector Rp. Since themachining pass vector Rp is given by a Cartesian coordinate system(XYZ), the position command value Up is in the same Cartesian coordinatesystem (XYZ). On the contrary, the position detected value Sm is thedetected value in the radial direction and the thrust direction.Further, in the electrode driving section 308, as shown in FIG. 1 andFIG. 2, four radial electromagnets are arranged in the upper section,and four radial electromagnets in the lower section and two thrustelectromagnets are arranged, thereby driving the tool electrode.Accordingly, in the electrode driving control section 306, the positioncommand values Up corresponding to the radial direction and the thrustdirection and for which coordinate conversion is not executed aredetermined, the determined values are compared with the positiondetected value Sm, and the current command value Uc to be output to thecurrent amplifier 307 is determined based on the result of thecomparison. The current command value Uc is given to eight currentamplifiers in the radial electromagnet section 107 and 108, and twocurrent amplifiers in the thrust electromagnet sections 111 and 112.

[0045]FIG. 4 is a diagram which shows an operation content of the systemshown in FIG. 3. The gap control between the electrode and a workpieceis generally achieved by a software process applied by a microcomputer,and FIG. 4 shows k th process. S401 corresponds to a process in themachining state detecting section 302 in FIG. 3, and the state variabley of the electric discharge machining process is detected, for example,as an average gap voltage ym(k). Next, in step S402, a deviation e(k) isdetermined from the average gap voltage ym(k) and the reference value r.That is, S402 corresponds to a process of determining the deviation fromthe outputs of the machining state detecting section 302 and thereference value setting section 303 shown in FIG. 3. Next, in step S403,a proportional+integral compensation is applied to the deviation e(k),and a command value Up(k) is determined on the basis of an amountobtained by the compensation and the machining pass vector Rp. Here, kpcorresponds to a proportional gain, ki corresponds to an integral gain,Up(k) corresponds to respective command values in the XYZ-axesdirections, and Up(k) is given by the Cartesian coordinate system.

[0046] In step S404, the coordinate is converted from Up(k) into theradial direction and the thrust direction, and respective referencevalues Rm(k) in the radial direction and the thrust direction aredetermined. Next, a deviation Em(k) is determined on the basis of thereference value Rm(k), and detected values Sm(k) from the radialdirection position detecting sections 109 and 110 and the thrustdirection position detecting section 113. Further, proportional+integralcompensation is applied to the deviation Em(k), and a command valueUc(k) to the current amplifier 307 is determined. Here, T is acoordinate conversion matrix, Kpm is a proportional gain, kim is anintegral gain, and a calculation in step S404 is described in a form ofmatrix calculation. The process in step S404 is executed in theelectrode driving control section 306 in FIG. 3.

[0047] As mentioned above, in the electric discharge machining apparatuscorresponding to the first embodiment of the present invention, inaccordance with the electrode driving section 105, since the structureis made such as to drive only the electrode mounting section 106mounting the tool electrode 101 thereto in the non-contact manner in theradial direction and the thrust direction by the radial electromagnetsections 107 and 108 and the thrust electromagnet sections 111 and 112,it is possible to restrict a mass increase of a section which isrequired to be driven together with the tool electrode 101.

[0048] Further, in the system for controlling a gap between the toolelectrode and the workpiece, since the structure is made such as todetect the average gap voltage ym(k) by the machining state detectingsection 302, determine the command value Up(k) in the XYZ coordinatesystem by which the tool electrode 101 should be driven on the basis ofthe detected value ym(k), the reference value r and the machining passvector Rp, determine the reference value Rm(k) to the radial drivingsection and the thrust driving section in the electrode driving section105, by executing coordinate conversion to the command value Up(k), andmove the tool electrode 101 in the radial direction and the thrustdirection by the electrode driving section 105 in accordance with thereference value Rm(k), it is possible to coincide the detected valueym(k) with the reference value r at the same time of moving the toolelectrode 101 in the XYZ directions by the electrode driving section 105in accordance with the machining pass vector Rp, thereby achieving astable machining state. Accordingly, it is possible to achieve the highspeed response in the X-axis, Y-axis and Z-axis directions, and it ispossible to always maintain the stable machining state even when themachining state irregularly changes. Therefore, it is possible toachieve an improvement of the machining speed, and further animprovement of the machining accuracy.

[0049] In the above, the electromagnet is used in the radial drivingsection and the thrust driving section in the electrode driving section105. However, the electrode driving section 105 may be structured suchthat the thrust driving section also includes a permanent magnet tocancel weights of the tool electrode 101 and the electrode mountingsection 106, and thus the electrode driving section 105 includes boththe electromagnet and the permanent magnet. As a result, it is possibleto achieve the same effects as that mentioned above.

[0050] Further, the instance in which the system for controlling a gapbetween a tool electrode and a workpiece is structured by detecting themachining state by the average gap voltage is described, however, thesystem may be structured by detecting the machining state by a ignitiondelay time of an electric discharge pulse, and it is possible to achievethe same operational effects as mentioned above.

[0051] Further, it is explained above that both the proportional and theintegral compensation are executed. However, a feed back controlincluding proportional compensation, proportional, integral, anddifferential compensation and the like may be employed. On the otherhand, a feed forward control system or the like may be employed. Sameeffects can be achieved by employing any of these control systems.

[0052] Second Embodiment:

[0053]FIG. 5 is a schematic view which shows an electric dischargemachining apparatus corresponding to a second embodiment of the presentinvention. In FIG. 5, reference numerals 101 to 104, 501 to 507 and 1202are the same as the structures shown in the conventional art. Further,reference numerals 118, 119 and 120 are the same as the structures inthe first embodiment. Further, reference numeral 508 denotes a controlapparatus giving a command value to an current amplifier 118 whichsupplies current to the servo amplifier 1202 and the electromagnetsection of the electrode driving section 105, and the machining powersupply 119. In FIG. 5, the position adjusting section constituted by thehead section 501, the head driving section 502, the column section 503,the column driving section 504, the saddle section 505 and the saddledriving section 506 adjusts the position of the electrode drivingsection 105. The electrode driving section 105 is mounted to the headsection 501, the head section 501 is driven in the Z-axis direction bythe head driving section 502, the head driving section 502 is mounted tothe column section 503, the column section 503 is driven in the Y-axisdirection by the column driving section 504, the column driving section504 is mounted to the saddle section 505, and the saddle section 505 isdriven in the X-axis direction by the saddle driving section 506.

[0054] A driving stroke of the electrode driving section 105 is betweenseveral hundred μm to 1 mm. When the driving stroke is insufficient forthe machining, it is possible to expand a substantial driving stroke byharmoniously operating the electrode driving section 105 and theposition adjusting section constituted by the head driving section 502,the column driving section 504 and the saddle driving section 506 so asto adjust the relative position between the tool electrode 101 and theworkpiece 102.

[0055]FIG. 6 is a block diagram of a system for controlling a gapbetween a tool electrode and a workpiece which control an electricdischarge machining state in the electric discharge machining apparatuscorresponding to the second embodiment of the present invention. In FIG.6, the same reference numerals as those in FIG. 3 denote thecorresponding elements, and a description thereof will be omitted.Reference numeral 601 denotes a coordination machining control section,and reference numeral 602 denotes a position adjusting apparatussection, which corresponds to the conventional XYZ driving apparatussection. Upl indicates a command value to the electrode drivingapparatus section 309, Ups indicates a command value to the positionadjusting apparatus section 602, and Mp indicates an electrode operatingamount operated by the electrode driving apparatus section 309 and theposition adjusting apparatus section 602. The command value Upl to theelectrode driving section 309 and the command value Ups to the positionadjusting apparatus section 602 are determined by the coordinationmachining control section 601 on the basis of the deviation e and themachining pass vector Rp.

[0056] That is, in this system of the electric discharge machiningapparatus corresponding to the first embodiment, the machining processis controlled by adjusting the position of the tool electrode 101 by theelectrode driving apparatus section 309 on the basis of the commandvalue Up determined by the machining control section 305, on thecontrary, in the gap control system in the electric discharge machiningapparatus corresponding to the second embodiment, the machining processis controlled by adjusting the position of the tool electrode 101 by theelectrode driving apparatus section 309 and the position adjustingapparatus section 602 on the basis of the command values Upl and Upsdetermined by the coordination machining control section 601. Theposition adjusting apparatus section 602 can easily achieve a drivingstroke equal to or more than some hundreds mm, for example, by beingstructured by an AC motor and a ball screw or a linear motor.Accordingly, even in a situation that requires machining exceeding thedriving stroke of the tool electrode 101 driven by the electrode drivingapparatus section 309, it is possible to expand the driving stroke ofthe tool electrode 101 by adjusting the relative position between theelectrode 101 and the workpiece 102 by the position adjusting apparatussection 602.

[0057]FIG. 7 is a block diagram which shows the coordination machiningcontrol section 601 in detail. In the drawing, reference numeral 603denotes a first computing section, reference numeral 604 denotes asecond computing section, and reference numeral 605 denotes a thirdcomputing section. In the first computing section 603, in order tocontrol the machining process by the electrode driving apparatus section309 and the position adjusting apparatus section 602, the command valueUp in the XYZ coordinate system by which the tool electrode 101 shouldbe driven is determined on the basis of the deviation e determined fromthe reference value r and the detected value ym and the machining passvector Rp. In the second computing section 604, the command value Upl tothe electrode driving apparatus section 609 is determined on the basisof the command value Up. Further, in the third computing section 605,the command value Ups to the position adjusting apparatus section 602 isdetermined on the basis of the command value Up. The processes in thefirst computing section 603, the second computing section 604 and thethird computing section 605 will be explained in detail below.

[0058]FIG. 8 shows an operation content of the gap control system shownin FIG. 6. The gap control is generally achieved by the software processapplied by the microcomputer, and FIG. 8 shows k th time process. InFIG. 8, S401 to S403 are the same as those shown in the firstembodiment. S401 corresponds to a process in the machining statedetecting section 302 in FIG. 6, and the state variable y of theelectric discharge machining process is detected, for example, as anaverage gap voltage ym(k). Next, in step S402, a deviation e isdetermined from the average gap voltage ym(k) and the reference value r.S403 corresponds to a process in the first computing section 603 in FIG.7. That is, a proportional+integral compensation is applied to thedeviation e(k), and a command value Up(k) is determined on the basis ofan amount obtained by the compensation and the machining pass vector Rp.Here, kp corresponds to a proportional gain, ki corresponds to anintegral gain, Up(k) corresponds to respective command values in theXYZ-axes directions, and Up(k) is given by the Cartesian coordinatesystem (XYZ). S701 corresponds to a process in the second computingsection 604 and the third computing section 605 in FIG. 7. That is, aprocess of filtering Up(k) by a digital filter Fpl(z⁻¹) so as todetermine the command value Upl(k) is executed by the second computingsection 604. Further, a process of filtering Up(k) by a digital filterFps(z⁻¹) so as to determine a command value Ups(k) is executed by thethird computing section 605. Characteristics of the digital filterFps(z⁻¹) and the digital filter Fpl(z⁻¹) are determined so that theposition adjusting apparatus can compensate the progress of themachining while the electrode driving apparatus stably controls themachining state. For example, the digital filter Fpl(z⁻¹) is set to alow pass filter characteristic in which a cutoff frequency is about someHz, or to a band pass filter characteristic in which a pass band isapproximately between some Hz to some hundreds Hz, and the digitalfilter Fps(z⁻¹) is set to a low pass filter characteristic in which acutoff frequency is about some Hz. Here, Upl(k) and Ups(k) areconstituted by the respective command value in the XYZ-axes directions.S403 and S701 mentioned above correspond to the process in thecoordination machining control section 601 in FIG. 6. S702 correspondsto a process in the electrode driving apparatus section 309 in FIG. 6,and more strictly a process in the electrode driving control section 306in FIG. 3. That is, in step S702, the coordinate is converted fromUpl(k) into the radial direction and the thrust direction, andrespective reference values Rm(k) in the radial direction and the thrustdirection are determined. Next, a deviation Em(k) is determined on thebasis of the reference value Rm(k), and detected values Sm(k) from theradial direction and thrust direction position detecting section.Further, proportional+integral compensation is applied to the deviationEm(k), and a command value Uc(k) to the current amplifier is determined.Here, T is a coordinate conversion matrix, Kpm is a proportional gain,kim is an integral gain, and a calculation in step S702 is described ina form of matrix calculation. The software process mentioned above isachieved in the control apparatus 508 in FIG. 5.

[0059] As mentioned above, the electric discharge machining apparatuscorresponding to the second embodiment of the present invention includesthe coordination machining control section 601 which controls themachining process by coordinating the electrode driving apparatussection 309 and the position adjusting apparatus section 602 to adjustthe position of the tool electrode 101. As a result, it is possible toachieve a more stable machining state by the electrode driving apparatussection 309 and it is simultaneously possible to adjust the position ofthe electrode driving apparatus in correspondence to the progress of themachining by the position adjusting apparatus section 602, so that it ispossible to achieve an improvement of the machining speed, and furtheran improvement of the machining accuracy without being limited by thedriving stroke of the electrode driving section.

[0060] In the above, the structure is made such that the electrodedriving section 105 is driven in the XYZ-axes directions by the positionadjusting section constituted by the head driving section 502, thecolumn driving section 504 and the saddle driving section 506, however,the structure may be made such that the workpiece 102 is driven in XYdirections by a XY table in place of the column driving section 504 andthe saddle driving section 506, and the electrode driving section 105 ismounted to the head section 501 and is driven in a Z-axis direction bythe head driving section 502.

[0061] Further, in the above, the instance in which the software processof the gap control is processed by one microcomputer is explained,however, the gap control may be achieved by executing, for example, theprocess in step S702 in the electrode driving apparatus section 309 byusing another microcomputer in which it is possible to obtain the sameoperational effects as mentioned above.

[0062] Further, in the above the instance in which the gap controlsystem is structured by detecting the machining state by the average gapvoltage is explained, however, the gap control system may be structuredby detecting the machining state by an ignition delay time of anelectric discharge pulse.

[0063] Further, in the above, the instance in which theproportional+integral compensation is, executed is explained, however, afeed back control system such as a proporational compensation, aproportional+integral+differental compensation and the like, or a feedforward control system or the like may be structured.

[0064] Third Embodiment:

[0065]FIG. 9 is a block diagram of a part of a gap control system whichcontrols machining state in an electric discharge machining apparatuscorresponding to a third embodiment of the present invention, that is, acoordination machining control section which is different from thatshown in the second embodiment. In FIG. 9, functions of e, Rp, 603 to605, Upl and Ups are the same as the structures shown in the secondembodiment. Reference numeral 801 denotes a coordination machiningcontrol section, reference numeral 802 denotes a jump motion settingsection, reference numeral 803 denotes a jump motion control section,and reference numeral 804 denotes a mode switching section whichswitches between a jump motion mode and a machining servo mode.

[0066] Rj corresponds to a jump motion set value such as a jump updistance, a jump down time, a jump speed and the like which are set bythe jump motion setting section 802, Uj corresponds to a jump motioncommand value which is generated by the jump motion control section 803on the basis of the jump motion set value Rj, swj corresponds to asignal applied to the mode switching section 804 which switches betweenthe jump mode and the machining servo mode, and cj corresponds to asignal applied to the second computing section 604 which keeps thecommand value Upl to the electrode driving apparatus constant during thejump motion mode. That is, the jump motion is executed by the positionadjusting apparatus section 602, and the machining control at themachining servo mode is executed by the coordinating driving apparatussection 309 and the position adjusting apparatus section 602 in aharmonious manner.

[0067] As mentioned above, in accordance with the electric dischargemachining apparatus corresponding to the third embodiment of the presentinvention, since there are provided the jump motion control section 803,the coordination machining control section 801 having the mode switchingsection 804 which switches between the jump motion and the machiningservo, and the jump motion setting section 802 in addition to the firstcomputing section 603, the second computing section 604 and the thirdcomputing section 605 which constitute the electric discharge machiningapparatus corresponding to the second embodiment, the electrode drivingapparatus section 309 and the position adjusting apparatus section 602harmoniously execute the machining control in the same manner as that ofthe electric discharge machining apparatus corresponding to the secondembodiment at the machining servo mode, and the position adjustingapparatus section 602 executes the jump motion based on the jump motionset value Rj set by the jump motion setting section 802 at the jumpmotion mode. Accordingly, it is possible to achieve a stable machiningstate with the electrode driving apparatus section 309 capable ofresponding at high speed and to adjust the position of the electrodedriving apparatus in correspondence to the progress of the machining bythe position adjusting apparatus section 602. As a result, it ispossible to improve the machining speed, and further the machiningaccuracy without being limited by the driving stroke of the electrodedriving section. Further, it is possible to machine without beinglimited by the driving stroke of the electrode driving apparatus section309 and forcibly discharging the debris staying in the machining gapwith the jump motion by the position adjusting apparatus section 602. Asa result, it is possible to improve the machining speed and themachining accuracy even when the machining depth is deep.

[0068] Forth Embodiment:

[0069]FIG. 10 is a block diagram of a part of a gap control system whichcontrols machining state in an electric discharge machining apparatuscorresponding to a forth embodiment of the present invention, that is, acoordination machining control section which is different from thatshown in the second embodiment. In FIG. 10, meanings of e, Upl and Upsare the same as those shown in the second embodiment. Reference numeral901 denotes a coordination machining control section, reference numeral902 denotes a planetary motion locus setting section, reference numeral903 denotes a planetary motion control section, reference numeral 904denotes a machining pass setting section, and reference numeral 905denotes a machining control section.

[0070] Rv corresponds to a planetary motion locus vector set in theplanetary motion locus setting section 902, Rp corresponds to amachining pass vector set in the machining pass setting section 904, andcv corresponds to a signal for synchronizing the planetary motion locuswith the machining pass. In the planetary motion machining, the toolelectrode 101 is moved in an expanded manner so as to form a circularshape, a square shape or the like on a two-dimensional plane at amagnitude between some μm and some hundreds μm in synchronous with apredetermined depth, or moved in an expanded manner on athree-dimensional curved surface at a predetermined position. Theplanetary motion locus vector Rv constituted by the expanded motionbetween some μm and some hundreds μm is set in the planetary motionlocus setting section 902, and the machining pass vector Rp is set inthe machining pass setting section 904 to move the tool electrode 101 toa predetermined depth or a predetermined position

[0071] Further, the command value Upl to the electrode driving apparatussection 309 is determined in the planetary motion control section 903 onthe basis of the deviation e and the planetary motion locus vector Rv,the tool electrode is moved in the expanded manner by the electrodedriving section, and the planetary motion machining is achieved whilemaintaining the stable machining state. Further, the command value Upsto the position adjusting apparatus section 602 is determined in themachining control section 904 on the basis of the deviation e and themachining pass vector Rp, and is moved to the predetermined depth or thepredetermined position while maintaining the stable machining state. Atthis time, the planetary motion control section 903 and the machiningcontrol section 904 are synchronized by the signal cv.

[0072] As mentioned above, in accordance with the electric dischargemachining apparatus corresponding to the forth embodiment of the presentinvention, since there are provided the coordination machining controlsection 901 including the planetary motion control section 903 and themachining control section 905, the planetary motion locus settingsection 902 and the machining pass setting section 904, it is possibleto adjust the position of the tool electrode 101 on the basis of themachining pass vector Rp set in the machining pass setting section 904by the position adjusting apparatus section 602, and it is possible toexecute the planetary motion on the basis of the planetary motion locusvector Rv set in the planetary motion locus setting section 902 by theelectrode driving apparatus section 309 capable of executing the highspeed response. Accordingly, it is possible to achieve the planetarymotion maintaining a stable machining state by the electrode drivingapparatus section 309 capable of executing the high speed response, andit is possible to achieve an improvement of the machining speed and animprovement of the machining accuracy.

[0073] In the above, the structure is made such that the planetarymotion control section 903 is provided in the coordination machiningcontrol section 901 and the planetary motion machining is executed bythe electrode driving section, however, it may be made such that theplanetary motion control section 903 and the jump motion control section803 described in the third embodiment are simultaneously provided in thecoordination machining control section 901, and the planetary motionmachining is executed while executing the jump motion by the positionadjusting section.

[0074] Fifth Embodiment:

[0075]FIG. 11 is an outline schematic view which shows an electrodedriving section in an electric discharge machining apparatuscorresponding to a fifth embodiment of the present invention. In FIG.11, reference numerals 106 to 117 are the same as those shown in thefirst embodiment. Reference numeral 1001 denotes a motor section whichrotates the electrode mounting section 106, reference numeral 1002denotes an electromagnetic section which applies a torque to the motorsection 1001, reference numeral 1003 denotes a rotation detectingsection which detects at least one or both of an angle of rotation andan angular velocity of rotation of the electrode mounting section 106,and reference numeral 1004 denotes an electrode driving section. Asmentioned above, a rotation driving section is constituted by the motorsection 1001 and the electromagnet section 1002.

[0076]FIG. 12 is a block diagram of a part of a gap control system inthe electric discharge machining apparatus having the electrode drivingsection shown in FIG. 11, that is, an electrode driving apparatussection which is different from the electrode driving apparatus section309 shown in FIG. 3 of the first embodiment. In FIG. 12, meanings of e,Up, Mp, 306, 307, Uc and Sm are the same as those shown in the firstembodiment. Reference numeral 1101 denotes an electrode drivingapparatus section, reference numeral 1102 denotes a rotation settingsection, reference numeral 1103 denotes a rotation control section, andreference numeral 1104 denotes a current amplifier. Reference numeral1105 corresponds to the electrode driving section 1004 in FIG. 11. InFIG. 12, Rr corresponds to a rotation set value of at least one or bothof the angle of rotation and the angular velocity of rotation, Srcorresponds to a detected value detected by the rotation detectingsection 1003, and Ur corresponds to a command value to the currentamplifier.

[0077] Here, it is assumed that the angle of rotation Rr of the toolelectrode 101 is set by the rotation setting section 1102. The rotationcontrol section 1103 determines the command value Ur to the currentamplifier 1104 so that the detected value Sr detected in the rotationdetecting section 1003 coincides with the set value Rr, and rotates thetool electrode 101 at only a predetermined angle. Further, when theangular velocity of rotation Rr of the tool electrode 101 is set by therotation setting section 1102, the rotation control section 1103determines the command value Ur to the current amplifier 1104 so thatthe detected value Sr detected in the rotation detecting section 1003coincides with the set value Rr, and controls the angular velocity ofrotation of the tool electrode 101.

[0078] As mentioned above, in accordance with the electric dischargemachining apparatus corresponding to the fifth embodiment of the presentinvention, since there are provided the electrode driving section 1004constituted by the motor section 1001 which rotates the electrodemounting section 106, the electromagnet section 1002 which applies thetorque to the motor section 1001, and the rotation detecting section1003 which detects at least one or both of the angle of rotation and theangular velocity of rotation of the electrode mounting section 106, andthe electrode driving apparatus section 1101 constituted by the rotationsetting section 1102, the rotation control section 1103 and the currentamplifier 1104, in addition to the structures of the electrode drivingsection 105 and the electrode driving apparatus section 309 in theelectric discharge machining apparatus corresponding to the firstembodiment, it is possible to rotate the tool electrode 101 at apredetermined angle on the basis of the angle of rotation Rr set by therotation setting section 1102, or it is possible to control the angularvelocity of rotation of the tool electrode 101 on the basis of theangular velocity of rotation Rr set by the rotation setting section1102. Accordingly, it is possible to identify the rotational position ofthe tool electrode 101, to achieve the machining while rotating the toolelectrode 101 and to maintain a stable machining state with theelectrode driving apparatus section 1101 which can respond at highspeed. As a result, it is possible to achieve an improvement ofmachining speed and an improvement of machining accuracy.

[0079] The electrode driving apparatus section 1101 mentioned above mayconstruct the electric discharge machining apparatus in place of theelectrode driving apparatus section in the electric discharge machiningapparatus corresponding to the second, third, and fourth embodiments.

[0080] Sixth Embodiment:

[0081]FIG. 13 is a schematic view which shows an outline of an electricdischarge machining apparatus corresponding to a sixth embodiment of thepresent invention. In FIG. 13, reference numerals 102 to 104 are thesame as those shown in the conventional art. Further, reference numerals111 to 113 and 119 to 122 are the same as those shown in the firstembodiment. Further, reference numeral 1501 denotes a wire-likeelectrode, reference numeral 1502 denotes a through hole section whichinserts the wire-like electrode 1501 therethrough, reference numeral1503 denotes an electrode holding/feeding section which holds or feedsthe wire-like electrode 1501, reference numeral 1504 denotes anelectrode guide which guides the wire-like electrode 1501, referencenumeral 1505 denotes an electrode mounting section having the electrodeholding/feeding section 1503 at a front end and having the through holesection 1502 at a center, reference numeral 1506 denotes a power supplysection which supplies a machining energy from the machining powersupply 119, reference numerals 1507 and 1508 denote a bearing sectionwhich supports the electrode mounting section 1505 in XY surface,reference numeral 1509 denotes an electrode driving section constitutedby the electrode holding/feeding section 1503 and the thrustelectromagnet sections 111 and 112, reference numeral 1510 denotes acurrent amplifier which supplies current to the electromagnet sections111 and 112 of the electrode driving section 1509, and reference numeral1511 denotes a current amplifier which supplies current to the electrodeholding/feeding section 1503.

[0082] The electric discharge machining apparatus shown in FIG. 13 cancontinuously and effectively execute a hole machining by using thewire-like electrode 1501. That is, at first, the wire-like electrode1501 is supplied to the through hole section 1502. The wire-likeelectrode 1501 is fed by the electrode holding/feeding section 1503, andthe electrode is held in a state such that the tip of the electrode isfed out from the electrode guide 1504 for a predetermined amount. Inthis state, machining power is supplied to the wire-like electrode 1501and the workpiece 102 by the machining power supply 119, and themachining is executed while the controlling the gap between the toolelectrode and the workpiece with the help of the machining statedetecting apparatus 120, the electrode driving section 1509, and thecontrol apparatus 121. In the electric discharge machining, thewire-like electrode 1501 is consumed every one hole machining, and alength of the electrode protruding out from the electrode guide 1504 isreduced. Accordingly, when the length of the electrode protruding outfrom the electrode guide 1504 is insufficient to execute the next holemachining, the wire-like electrode 1501 is again fed by the electrodeholding/feeding section 1503, the electrode is held in a state offeeding out the leading end of the electrode from the electrode guide1504 at a predetermined amount, and the next hole machining is executed.FIG. 14 is a block diagram of a gap control system which controls theelectric discharge machining state in the electric discharge machiningapparatus shown in FIG. 13, and an electrode supply control system.

[0083] In FIG. 14, the same reference numerals as those in FIG. 3 denotethe same or corresponding elements, and a description thereof will beomitted. Reference numeral 1601 denotes a machining pass settingsection, reference numeral 1602 denotes a machining control section,reference numeral 1603 denotes a thrust driving control section,reference numeral 1604 denotes a current amplifier section, referencenumeral 1605 denotes a thrust driving section, reference numeral 1606denotes a thrust driving apparatus section constituted by the thrustdriving control section 1603 and the current amplifier section 1604 andthe thrust driving section 1605, reference numeral 1607 denotes anelectrode supply amount setting section, reference numeral 1608 denotesan electrode supply control section, reference numeral 1609 denotes acurrent amplifier section, reference numeral 1610 denotes an electrodeholding/feeding section, and reference numeral 1611 denotes an electrodeholding/feeding apparatus section constituted by the electrode supplyamount setting section 1607, the electrode supply control section 1608,the current amplifier section 1609 and the electrode holding/feedingsection 1610. The current amplifier section 1604 corresponds to thecurrent amplifier 1510, the thrust driving section 1605 corresponds tothe electrode driving section 1509 excluding the electrodeholding/feeding section 1503, the current amplifier section 1609corresponds to the current amplifier 1511, and the electrodeholding/feeding section 1610 corresponds to the electrodeholding/feeding section 1503, respectively. Further, the reference valuesetting section 303, the machining pass setting section 1601, themachining control section 1602, the thrust driving control section 1603,the electrode supply amount setting section 1607 and the electrodesupply control section 1608 are constructed in the control apparatus121. Further, rp indicates a machining depth set in the machining passsetting section 1601, zp indicates a position command value to thethrust driving control section 1603, Umc indicates a current commandvalue to the current amplifier section 1604, Imc indicates a currentamount supplied to the thrust driving section 1605, Smm indicates aposition detected value obtained from the thrust driving section 1606,rl indicates an electrode supply amount set in the electrode supplyamount setting section 1607, Usc indicates a current command value tothe current amplifier section 1609, Isc indicates a current amountsupplied to the electrode holding/feeding section 1610, Ssm indicates aposition detected value obtained from the electrode holding/feedingsection 1610, and Mp indicates an electrode position operating amountoperated by the thrust driving section 1605 and the electrodeholding/feeding section 1610.

[0084] The position command value zp to the thrust driving controlsection 1603 in the thrust driving apparatus section 1605 is determinedin the machining control section 1602 on the basis of the deviation eand the machining pass rp. Since the machining pass rp is given by theCartesian coordinate system (XYZ), the position command value zp is inthe same Cartesian coordinate system (XYZ). Further, the positiondetected value Smm corresponds to a detected value in the thrustdirection (z direction). Further, in the thrust driving section 1605,the tool electrode is driven by two thrust electromagnets as shown inFIG. 13. Accordingly, in the thrust driving control section 1603, thecurrent command value Umc to the current amplifier section 1604 isdetermined by comparing the position command value zp with the positiondetected value Smm. The current command value Umc is given to twocurrent amplifiers for the thrust electromagnet sections 111 and 112.

[0085] On the contrary, the current command value Usc to the currentamplifier section 1609 in the electrode holding/feeding apparatussection 1611 is determined in correspondence to the state of holding orfeeding the electrode while referring to the electrode supply amount rlobtained from the electrode supply amount setting section 1607 by theelectrode supply control section 1608 and the position detected valueSsm obtained from the electrode holding/feeding section 1610, and thecurrent amount Isc is supplied to the electrode holding/feeding section1610 in correspondence to the command value.

[0086]FIG. 15 is a flow chart which shows an operation content of theelectrode supply control system shown in FIG. 14. The electrode supplycontrol system is generally achieved by a software process applied by amicrocomputer. Since the operation content of the gap control systemshown in FIG. 14 is the same as the control in the thrust direction inthe first embodiment, a description thereof will be omitted. In FIG. 15,in step S1701, it is determined whether it is in the electrode feedingmode or the electrode holding mode at present. When it is in theelectrode holding mode, in step S1705, the state of holding the toolelectrode is maintained. When it is in the electrode feeding mode, it ismeasured or estimated in step S1702 how long the tip of the toolelectrode protrudes out from the electrode guide 1504. This quantity maybe measured, for example, by using the following process. For example,the tip of the electrode by the thrust driving apparatus section 1606 isdriven until it is in contact with a certain reference position, andsince the initial position and the final position are known, it ispossible to determine the quantity. Further, this quantity may beestimating, for example, by using the following process. For example,amount of consumption of an electrode may be measured beforehand fordifferent machining condition, and by subtracting the consumption amountfor the current machining condition from the electrode supply amount rlit is possible to determine the quantity. In step S1703, an amount to beactually fed out is determined on the basis of a value al obtained instep S1702 and the electrode supply amount rl, and in step S1704, thetool electrode is fed out by the electrode holding/feeding section 1610at a determined amount. Further, in step S1705, the tool electrode isheld.

[0087] As mentioned above, in the electric discharge machining apparatuscorresponding to the sixth embodiment of this invention, in accordancewith the electrode driving section 1509, since the structure is madesuch as to drive the electrode holding/feeding section 1503 which holdsthe wire-like electrode 1501 and the electrode mounting section 1505 ina non-contact manner in the thrust direction by the thrust electromagnetsection 111 and the thrust electromagnetic section 112, it is possibleto restrict a mass increase of the section which should be driventogether with the wire-like electrode 1501. Then, it is possible toachieve a high response in the thrust direction, and it is possible toalways maintain a stable machining state even when the machining stateirregularly changes. Accordingly, it is possible to achieve animprovement of machining speed, and further an improvement of machiningaccuracy. Further, in accordance with the electrode holding/feedingsection 1503, since it is possible to automatically hold or feed thewire-like electrode 1501, it is possible to continuously and effectivelyexecute the hole machining.

[0088]FIG. 16 is a schematic view which shows an outline of acharacteristic section in another electric discharge machining apparatuscorresponding to the sixth embodiment of the present invention. In FIG.16, reference numeral 1801 denotes a bobbin around which the wire-likeelectrode 1501 is wound, reference numeral 1802 denotes a tool electrodesupply section which feeds out the wire-like electrode 1501, andreference numeral 1803 denotes an electrode cutting section which cutsthe wire-like electrode 1501 at a suitable length. When the machining iscontinuously executed and the wire-like electrode 1501 is consumed so asto be short, the wire-like electrode 1501 is automatically inserted tothe through hole section 1502 from the bobbin 1801 by the tool electrodesupply section, and is cut by the electrode cutting section 1803 afterbeing fed out at a predetermined length. Then, the electrode is held ina state in which the electrode is fed out at the predetermined lengthfrom the electrode guide 1504 by the electrode holding/feeding section1503 to prepare for the next machining.

[0089] As mentioned above, in accordance with another electric dischargemachining apparatus corresponding to the sixth embodiment of thisinvention, it is possible to automatically supply the tool electrode bythe bobbin 1801 around which the wire-like electrode is wound, the toolelectrode supply section 1802, and the electrode cutting section 1803,it is possible to automatically replace the electrode at a time when thetool electrode is consumed, and it is possible to automatically executethe continuous hole machining.

[0090] In the above, the structure is made such as to drive thewire-like electrode 1501 in a non-contact manner in the thrust directionby the electrode driving section 1509, however, it is possible tocombine with the position adjusting section capable of adjusting theposition of the electrode driving section 1509 in the X-axis direction,the Y-axis direction and the Z-axis direction like the electricdischarge machining apparatus corresponding to the second embodimentwhere it is possible to obtain the same effects as mentioned above andit is possible to expand a substantial driving stroke.

[0091] Further, in the above, the structure is made such as to drive thewire-like electrode 1501 in a non-contact manner in the thrust directionby the electrode driving section 1509, however, a rotation drivingsection which rotates the electrode mounting section 1505 like theelectric discharge machining apparatus corresponding to the fifthembodiment may be provided where it is possible to obtain the sameeffect as mentioned above, and it is possible to achieve a more stablemachining by executing the machining while rotating the electrode whenthe hole machining is employed.

[0092] Industrial Applicability

[0093] The present invention is applied to the electric dischargemachining apparatus, restricts the mass increase of the section whichshould be driven together with the tool electrode, and achieves the highspeed response in the X-axis, the Y-axis and the Z-axis, whereby it ispossible to improve the machining speed and the machining accuracy andit can be effectively utilized for the hole machining.

1. An electric discharge machining apparatus comprising: an electrodemounting unit which mounts a tool electrode; an electrode driving unithaving a radial driving unit which drives the electrode mounting unit ina non-contact manner in a radial direction and a thrust driving unitwhich drives the electrode mounting unit in a non-contact manner in athrust direction; a machining state detecting unit which detects anelectric discharge machining state to obtain a detected value; areference value setting unit which sets a reference value to control theelectric discharge machining state; a machining pass setting unit whichsets a machining pass; and a machining control unit which adjusts aposition of the tool electrode by the electrode driving unit based onthe machining pass set by the machining pass setting unit, so that thedetected value detected by the machining state detecting unit coincideswith the reference value set by the reference value setting unit.
 2. Anelectric discharge machining apparatus comprising: an electrode mountingunit which mounts a tool electrode; an electrode driving unit having aradial driving unit which drives the electrode mounting unit in anon-contact manner in a radial direction and a thrust driving unit whichdrives the electrode mounting unit in a non-contact manner in a thrustdirection; a position adjusting unit which adjusts a position of theelectrode driving unit or a workpiece; a machining state detecting unitwhich detects an electric discharge machining state to obtain a detectedvalue; a reference value setting unit which sets a reference value tocontrol the electric discharge machining state; a machining pass settingunit which sets a machining pass; and a coordinating machining unitwhich adjusts a relative position between the tool electrode and theworkpiece by coordinating the electrode driving unit with the positionadjusting unit while taking into consideration the machining pass set bythe machining pass setting unit, so that the detected value detected bythe machining state detecting unit coincides with the reference valueset by the reference value setting unit.
 3. The electric dischargemachining apparatus according to claim 2, wherein the coordinatingmachining unit has a jump motion control unit which executes a jumpmotion by the position adjusting unit.
 4. The electric dischargemachining apparatus according to claim 2, wherein the coordinatingmachining control unit has a planetary motion control unit whichexecutes a planetary motion by the electrode driving unit.
 5. Theelectric discharge machining apparatus according to claim 2, wherein thecoordinating machining control unit has a jump motion control unit whichexecutes a jump motion by the position adjusting unit and a planetarymotion control unit which executes a planetary motion by the electrodedriving unit.
 6. The electric discharge machining apparatus according toclaim 1 or 2, wherein the electrode driving unit has a rotation drivingunit which rotates the electrode mounting unit and a rotation detectingunit which detects at least one or both of an angle of rotation and anangular velocity of rotation, and the machining control unit or thecoordinating machining control unit has a rotation control unit.
 7. Anelectric discharge machining method comprising: driving an electrodemounting unit which mounts a tool electrode in a non-contact manner in aradial direction and drive the electrode mounting unit in a non-contactmanner in a thrust direction; adjusting a position of a driving unit ora workpiece; and adjusting a position of the tool electrode with respectto the workpiece while taking into consideration a set machining pass,so that a detected value of an electric discharge machining statecoincides with a set reference value of the electric discharge machiningstate.
 8. An electric discharge machining method comprising: driving anelectrode mounting unit which mounts a tool electrode in a non-contactmanner in a radial direction and drive the electrode mounting unit in anon-contact manner in a thrust direction; adjusting a position of adriving unit or a workpiece; and adjusting a position of the toolelectrode with respect to the workpiece while taking into considerationa set machining pass, so that a detected value of an electric dischargemachining state coincides with a set reference value of the electricdischarge machining state by coordinating the driving unit with theadjusting unit.
 9. An electric discharge machining apparatus comprising:an electrode mounting unit having a through hole for inserting a wireelectrode therethrough and which has a holding and feeding mechanism forthe electrode; an electrode driving unit having a thrust driving unitwhich drives the electrode mounting unit at least in a non-contactmanner in a thrust direction; a machining state detecting unit whichdetects an electric discharge machining state as a detected value; areference value setting unit which sets a reference value to control theelectric discharge machining state; a machining control unit whichadjusts a position of the wire electrode by orchestrating the electrodedriving unit so that the detected value detected by the machining statedetecting unit coincides with the reference value set by the referencevalue setting unit; and an electrode supply control unit which adjustsholding or feeding of the electrode.
 10. The electric dischargemachining apparatus according to claim 9, comprising a wire electrodeautomatic supplying unit which automatically supplies the wire electrodeto the through hole provided in the electrode driving unit.
 11. Theelectric discharge machining apparatus according to claim 9 or 10,wherein the electrode driving unit has a rotation driving unit whichrotates the electrode mounting unit.